"In the past archaeologists haven't paid too much attention to molecular genetic evidence," said lead author Ted Goebel, an archaeologist at Texas A&M University in College Station.

"We have brought together two different fields of science, and it looks like they are coming up with the same set of answers."

The article, which is published in tomorrow's issue of the journal Science, shows that the first Americans came from a single Siberian population and ventured across the Bering land bridge connecting Asia and North America about 22,000 years ago.

The group got stuck in Alaska because of glacial ice, however, so humans probably didn't migrate down into the rest of the Americas until after 16,500 years ago, when an ice-free corridor in Canada opened up.